Plant enemies, such as herbivores that eat leaves, or diseases that invade and destroy plant tissue, are repelled by a suite of leaf traits that have evolved for plant defense. One of the most well-established forms of natural plant defenses are traits that recruit animals to defend the plant against its enemies in return for food and/or shelter. These reward traits can substantially reduce plant damage, but the benefits they confer can vary over different conditions, and some plant species have even evolved to lose reward-traits over time. This research focuses on understanding the dynamics of reward trait evolution using mite domatia (small structures on plant leaves that house beneficial mites). In the right context, mites housed in domatia protect the plant by cleaning the leaf surface of microbial pathogens and small herbivores. Mite domatia appear in ~24% the world's flowering plant families, and are found in many economically important groups, including coffee, cherries, and grapes. Grapes (genus Vitis), are especially interesting, as some species have mite-containing domatia that defend the leaves, while other species, including many of the most economically important grape species, do not. This research leverages the natural variation in domatia seen in wild grape species to understand how plant traits affect leaf communities. The genetic and environmental contexts in which plants successfully use beneficial mite populations to naturally defend themselves against pathogens and herbivores will be identified. The research will lead to a better understand of the interactions among grapes, their herbivores, beneficial arthropods, and the leaf microbiome. Data will be disseminated freely to the public and will have the potential to enhance grape agriculture and breeding, and potentially other important crop species. The project will also train a post-doctoral researcher and graduate student in diverse field and laboratory methods and analyses, and develop tools to better integrate research products in undergraduate biology classes.<br/><br/>This project will examine how leaf micro-structure impacts multi-trophic phyllosphere communities within and across Vitis species, and will investigate how phyllosphere dynamics can feedback to impact plant fitness. The presence/absence of domatia and related leaf-trait variation will be linked to abiotic conditions, genetic variation, consequences for leaf microbial and arthropod communities, and plant fitness. The investigators will integrate phylogenetic comparative modeling, niche and range reconstruction, comparative genomics, and large-scale field experiments to understand the historical, ecological, and genetic causes and consequences of leaf domatia trait variation in the diversification of Vitis species.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.